Method and apparatus for scheduling request operation of small cell enhancements in a wireless communication system

ABSTRACT

Methods and apparatuses are disclosed for scheduling request operation in a small cell in a wireless communication system. The method includes having a user equipment (UE) configured with a first serving cell and a second serving cell. The method further includes configuring the (UE) with a first scheduling request (SR) resource on a first physical uplink control channel and a second SR resource on a second physical uplink control channel. The method includes selecting, by the UE, the first SR resource to start a SR procedure in response to a trigger by a buffer status report (BSR), wherein an availability of the first SR resource is nearer to a timing of a triggering of the BSR than the availability of the second SR resource. Also, the method includes sending, by the UE, scheduling requests with the first SR resource on the first physical uplink control channel.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/807,103 filed on Apr. 1, 2013, the entire disclosure of which is incorporated herein by reference.

FIELD

This disclosure generally relates to wireless communication networks, and more particularly, to methods and apparatuses for small cell enhancement in a wireless communication system.

BACKGROUND

With the rapid rise in demand for communication of large amounts of data to and from mobile communication devices, traditional mobile voice communication networks are evolving into networks that communicate with Internet Protocol (IP) data packets. Such IP data packet communication can provide users of mobile communication devices with voice over IP, multimedia, multicast and on-demand communication services.

An exemplary network structure for which standardization is currently taking place is an Evolved Universal Terrestrial Radio Access Network (E-UTRAN). The E-UTRAN system can provide high data throughput in order to realize the above-noted voice over IP and multimedia services. The E-UTRAN system's standardization work is currently being performed by the 3GPP standards organization. Accordingly, changes to the current body of 3GPP standard are currently being submitted and considered to evolve and finalize the 3GPP standard.

SUMMARY

Methods and apparatuses are disclosed for scheduling request operation of a small cell in a wireless communication system. The method includes having a user equipment (UE) configured with a first serving cell and a second serving cell. The method further includes configuring the (UE) with a first scheduling request (SR) resource on a first physical uplink control channel and a second SR resource on a second physical uplink control channel. The method includes selecting, by the UE, the first SR resource to start a SR procedure in response to a trigger by a buffer status report (BSR), wherein an availability of the first SR resource is nearer to a timing of a triggering of the BSR than the availability of the second SR resource. Also, the method includes sending, by the UE, scheduling requests with the first SR resource on the first physical uplink control channel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram of a wireless communication system according to one exemplary embodiment.

FIG. 2 is a block diagram of a transmitter system (also known as access network) and a receiver system (also known as user equipment or UE) according to one exemplary embodiment.

FIG. 3 is a functional block diagram of a communication system according to one exemplary embodiment.

FIG. 4 is a functional block diagram of the program code of FIG. 3 according to one exemplary embodiment.

FIG. 5 is a diagram of scheduling request (SR) resource configuration according to one exemplary embodiment.

FIG. 6 is a diagram of scheduling request (SR) resource configuration according to one exemplary embodiment.

FIG. 7 is a diagram of scheduling request (SR) resource configuration according to one exemplary embodiment.

DETAILED DESCRIPTION

The exemplary wireless communication systems and devices described below employ a wireless communication system, supporting a broadcast service. Wireless communication systems are widely deployed to provide various types of communication such as voice, data, and so on. These systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), 3GPP LTE (Long Term Evolution) wireless access, 3GPP LTE-A or LTE-Advanced (Long Term Evolution Advanced), 3GPP2 UMB (Ultra Mobile Broadband), WiMax, or some other modulation techniques.

In particular, the exemplary wireless communication systems devices described below may be designed to support one or more standards such as the standard offered by a consortium named “3rd Generation Partnership Project” referred to herein as 3GPP, including Document Nos. TS36.321 v11.2.0 (2013-03) entitled “E-UTRA; MAC protocol specification,” TR36.392 v12.0.0 (2012-12) entitled “Scenarios and Requirements for Small Cell Enhancements for E-UTRA and E-UTRAN,” R2-130420 entitled “Protocol architecture alternatives for dual connectivity,” TR 36.913, RP-122033 entitled “New Study Item Description: Small Cell enhancements for E-UTRA and E-UTRAN—Higher-layer aspects,” and 3GPP R2-130570 entitled “Report of 3GPP TSG RAN WG2 meeting #72.” The standards and documents listed above are hereby expressly incorporated by reference in their entirety.

FIG. 1 shows a multiple access wireless communication system according to one embodiment of the invention. An access network 100 (AN) includes multiple antenna groups, one including 104 and 106, another including 108 and 110, and an additional including 112 and 114. In FIG. 1, only two antennas are shown for each antenna group, however, more or fewer antennas may be utilized for each antenna group. Access terminal 116 (AT) is in communication with antennas 112 and 114, where antennas 112 and 114 transmit information to access terminal 116 over forward link 120 and receive information from access terminal 116 over reverse link 118. Access terminal (AT) 122 is in communication with antennas 106 and 108, where antennas 106 and 108 transmit information to access terminal (AT) 122 over forward link 126 and receive information from access terminal (AT) 122 over reverse link 124. In a FDD system, communication links 118, 120, 124 and 126 may use different frequency for communication. For example, forward link 120 may use a different frequency then that used by reverse link 118.

Each group of antennas and/or the area in which they are designed to communicate is often referred to as a sector of the access network. In the embodiment, antenna groups each are designed to communicate to access terminals in a sector of the areas covered by access network 100.

In communication over forward links 120 and 126, the transmitting antennas of access network 100 may utilize beamforming in order to improve the signal-to-noise ratio of forward links for the different access terminals 116 and 122. Also, an access network using beamforming to transmit to access terminals scattered randomly through its coverage causes less interference to access terminals in neighboring cells than an access network transmitting through a single antenna to all its access terminals.

An access network (AN) may be a fixed station or base station used for communicating with the terminals and may also be referred to as an access point, a Node B, a base station, an enhanced base station, an eNB, or some other terminology. An access terminal (AT) may also be called user equipment (UE), a wireless communication device, terminal, access terminal or some other terminology.

FIG. 2 is a simplified block diagram of an embodiment of a transmitter system 210 (also known as the access network) and a receiver system 250 (also known as access terminal (AT) or user equipment (UE)) in a MIMO system 200. At the transmitter system 210, traffic data for a number of data streams is provided from a data source 212 to a transmit (TX) data processor 214.

In one embodiment, each data stream is transmitted over a respective transmit antenna. TX data processor 214 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide coded data.

The coded data for each data stream may be multiplexed with pilot data using OFDM techniques. The pilot data is typically a known data pattern that is processed in a known manner and may be used at the receiver system to estimate the channel response. The multiplexed pilot and coded data for each data stream is then modulated (i.e., symbol mapped) based on a particular modulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM) selected for that data stream to provide modulation symbols. The data rate, coding, and modulation for each data stream may be determined by instructions performed by processor 230.

The modulation symbols for all data streams are then provided to a TX MIMO processor 220, which may further process the modulation symbols (e.g., for OFDM). TX MIMO processor 220 then provides N_(T) modulation symbol streams to N_(T) transmitters (TMTR) 222 a through 222 t. In certain embodiments, TX MIMO processor 220 applies beamforming weights to the symbols of the data streams and to the antenna from which the symbol is being transmitted.

Each transmitter 222 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (e.g., amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. N_(T) modulated signals from transmitters 222 a through 222 t are then transmitted from N_(T) antennas 224 a through 224 t, respectively.

At receiver system 250, the transmitted modulated signals are received by N_(R) antennas 252 a through 252 r and the received signal from each antenna 252 is provided to a respective receiver (RCVR) 254 a through 254 r. Each receiver 254 conditions (e.g., filters, amplifies, and downconverts) a respective received signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding “received” symbol stream.

An RX data processor 260 then receives and processes the N_(R) received symbol streams from N_(R) receivers 254 based on a particular receiver processing technique to provide N_(T) “detected” symbol streams. The RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. The processing by RX data processor 260 is complementary to that performed by TX MIMO processor 220 and TX data processor 214 at transmitter system 210.

A processor 270 periodically determines which pre-coding matrix to use (discussed below). Processor 270 formulates a reverse link message comprising a matrix index portion and a rank value portion.

The reverse link message may comprise various types of information regarding the communication link and/or the received data stream. The reverse link message is then processed by a TX data processor 238, which also receives traffic data for a number of data streams from a data source 236, modulated by a modulator 280, conditioned by transmitters 254 a through 254 r, and transmitted back to transmitter system 210.

At transmitter system 210, the modulated signals from receiver system 250 are received by antennas 224, conditioned by receivers 222, demodulated by a demodulator 240, and processed by a RX data processor 242 to extract the reserve link message transmitted by the receiver system 250. Processor 230 then determines which pre-coding matrix to use for determining the beamforming weights then processes the extracted message.

Turning to FIG. 3, this figure shows an alternative simplified functional block diagram of a communication device according to one embodiment of the invention. As shown in FIG. 3, the communication device 300 in a wireless communication system can be utilized for realizing the UEs (or ATs) 116 and 122 in FIG. 1, and the wireless communications system is preferably the LTE system. The communication device 300 may include an input device 302, an output device 304, a control circuit 306, a central processing unit (CPU) 308, a memory 310, a program code 312, and a transceiver 314. The control circuit 306 executes the program code 312 in the memory 310 through the CPU 308, thereby controlling an operation of the communications device 300. The communications device 300 can receive signals input by a user through the input device 302, such as a keyboard or keypad, and can output images and sounds through the output device 304, such as a monitor or speakers. The transceiver 314 is used to receive and transmit wireless signals, delivering received signals to the control circuit 306, and outputting signals generated by the control circuit 306 wirelessly.

FIG. 4 is a simplified block diagram of the program code 312 shown in FIG. 3 in accordance with one embodiment of the invention. In this embodiment, the program code 312 includes an application layer 400, a Layer 3 portion 402, and a Layer 2 portion 404, and is coupled to a Layer 1 portion 406. The Layer 3 portion 402 generally performs radio resource control. The Layer 2 portion 404 generally performs link control. The Layer 1 portion 406 generally performs physical connections.

For LTE or LTE-A systems, the Layer 2 portion may include a Radio Link Control (RLC) layer and a Medium Access Control (MAC) layer. The Layer 3 portion may include a Radio Resource Control (RRC) layer.

In 3GPP TS36.321 v11.2.0, Scheduling Request (SR) operation with different Physical Uplink Control Channel resource is discussed as follows:

3GPP TR36.392 v12.0.0 discloses the following:

3GPP RP-122033 discloses the following:

In 3GPP TS36.300 discusses Carrier Aggregation (CA) as follows:

3GPP TS36.331 discloses the following about CA:

3GPP R2-130420 discusses protocol architecture alternatives for dual connectivity. Alternative U3 is a centralized PDCP termination and Alternative U4 is a distributed protocol termination for user plane. The pros and cons of these two alternatives are quoted below:

3GPP R2-130570 discusses scenarios and benefits of dual connectivity. It also addresses several protocol architecture alternatives for dual connectivity.

When UE is configured with both a Macro Cell and Small Cell, a PUCCH resource may be also needed for Small Cell due to uplink acknowledgement for DL data. However, PUCCH resource is typically configured for Macro Cell/PCell, it may be possible to configure PUCCH resources for scheduling requests on a Small Cell. Due to potential issues of non-ideal backhaul between the Macro Cell and the Small Cell, resource scheduling probably should be done in Small Cell itself.

Since some specific service and Control-plane data can be handled on Macro Cell and User-plane data can be handled on Small Cell, it may be possible that some service/data can be served simultaneously by both Macro and Small Cells.

If a UE is configured with more than one SR resource on PUCCH (which might be on the same Cell or different Cells), specific methods and/or coordination for the SR resources may be used to improve the efficiency of requesting UL resources of Macro or Small Cells.

In the following embodiments, a resource scheduler may be defined as resource allocator, Macro Cell/eNB, Small Cell/eNB, eNB, PCell or SCell. Macro Cell/eNB and Small Cell/eNB may be located in different geographical locations.

Since more than one SR resource is configured (on PUCCH) when a SR is triggered by BSR procedure, a user equipment (UE) would choose the nearest/upcoming configured (i.e., valid) SR resource to start a SR procedure. The UE would limit itself to the chosen SR resource and the UE may skip the other available SR resources. As shown in FIG. 5, SR1 and SR2 are two configured SR resources and SR1 is the nearest resource after BSR is triggered. The SR1 resource is chosen and the UE would send scheduling requests continuously with SR1 and skip SR2 resources.

In another method as shown in FIG. 6, the UE would use or attempt to use all valid SR resources. In one method, the UE could maintain independent SR procedures, for example, one SR procedure per Macro Cell (group) or Small Cell (group). In another method, a single SR procedure may be used for all valid Macro Cell or Small Cells.

According to one embodiment in which independent SR procedures are adopted per cell or cell group, all SR procedures would be considered complete upon a completion of any SR procedures. If one SR procedure fails (e.g., fails to achieve the SR maximum transmission times) while other SR procedures are still ongoing/pending, the Random Access (RA) procedure associated with the failed SR procedure would not be triggered because there are still chances on other SR resources. Accordingly, it is not urgent to trigger RACH procedure for requesting UL resources. However, the action of clearing any configured downlink assignments and uplink grants and/or notifying RRC to release PUCCH/SRS could be done (optionally, partially or completely).

In one embodiment, performing a RACH procedure could be considered after all SR procedures have failed. The RACH procedures may be performed on specific Macro and/or Small Cells. Alternatively, the RACH procedures may be performed on all Cells relevant to all the SR procedures.

If a common SR procedure is adopted, most actions would be similar to what is disclosed in 3GPP TS 36.321 V11.2.0. However, 3gPP TS 36.321 V11.2.0 does not contemplate how and/when to perform a RACH procedure.

In yet another method, SR resources may be configured (partially or completely) at the same time. In this method, the UE could choose a specific SR resource on a Macro or Small Cell or, alternatively, randomly select a SR resource as illustrate in FIG. 7. In FIG. 7, SR resource 1 and SR resource 2 may be configured on the different schedulers/Cells. In some instances, the locations of SR resource 1 and SR resource 2 are partially overlapping, which may result in SR1 and SR2 being sent at the same time from SR resource 1 and SR resource 2, respectively. As shown in FIG. 7, the UE may only choose to use SR resource 1 in the first scenario or only use SR resource 2 in the second scenario. In the third scenario shown in FIG. 7, the UE may decide to use both SR resources and prioritize SR resource 1 over SR resource 2 or vice versa (when they are configured at the same time). This rule can be configured by network or determined by UE itself. This method can be combined with the methods described above. When considering the possibility of simultaneously transmission on more than one PUCCH, the UE may depend on this restriction to determine which way to proceed. Taking the third case of FIG. 7 as an example, if the UE is able to use SR resource 1 and 2 at the same time, the UE may be able to send SR1 and SR2 at the same time. If UE is unable to use both SR resources 1 and 2 at the same time, the UE may choose either resource by according to a network configuration or by a UE decision.

Considering a scenario having a SR prohibit timer in one SR procedure with one SR resource in which a common SR procedure is adopted, the UE would need to differentiate/decide whether the SR resource is prohibited. In one embodiment, the UE would make this determination based on whether the scheduler (e.g., Macro or Small Cell) used the same SR resource (i.e., the previous and following SR resources are used for the same scheduler). If the SRs are sent to the same scheduler, then the following SR resource would be prohibited by a running prohibit timer.

As those skilled in the art will appreciate, the examples and descriptions disclose herein may be applied to more than two configured resources.

Referring back to FIGS. 3 and 4, the device 300 includes a program code 312 stored in memory 310. In one embodiment, the CPU 308 could execute program code 312 to execute one or more of the following: (i) to configure a user equipment (UE) with a first serving cell and a second serving cell; (ii) to configure the UE with at least a first and a second scheduling request (SR) resource on a physical uplink control channel; (iii) to select the first SR resource to start a SR procedure in response to a trigger by a buffer status report (BSR), wherein the first SR resource is nearer to the BSR than the second SR resource; and (iv) to send scheduling requests with the first SR resource.

In addition, the CPU 308 can execute the program code 312 to perform all of the above-described actions and steps or others described herein.

Various aspects of the disclosure have been described above. It should be apparent that the teachings herein may be embodied in a wide variety of forms and that any specific structure, function, or both being disclosed herein is merely representative. Based on the teachings herein one skilled in the art should appreciate that an aspect disclosed herein may be implemented independently of any other aspects and that two or more of these aspects may be combined in various ways. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, such an apparatus may be implemented or such a method may be practiced using other structure, functionality, or structure and functionality in addition to or other than one or more of the aspects set forth herein. As an example of some of the above concepts, in some aspects concurrent channels may be established based on pulse repetition frequencies. In some aspects concurrent channels may be established based on pulse position or offsets. In some aspects concurrent channels may be established based on time hopping sequences. In some aspects concurrent channels may be established based on pulse repetition frequencies, pulse positions or offsets, and time hopping sequences.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, processors, means, circuits, and algorithm steps described in connection with the aspects disclosed herein may be implemented as electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of the two, which may be designed using source coding or some other technique), various forms of program or design code incorporating instructions (which may be referred to herein, for convenience, as “software” or a “software module”), or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

In addition, the various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented within or performed by an integrated circuit (“IC”), an access terminal, or an access point. The IC may comprise a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, electrical components, optical components, mechanical components, or any combination thereof designed to perform the functions described herein, and may execute codes or instructions that reside within the IC, outside of the IC, or both. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

It is understood that any specific order or hierarchy of steps in any disclosed process is an example of a sample approach. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged while remaining within the scope of the present disclosure. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

The steps of a method or algorithm described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module (e.g., including executable instructions and related data) and other data may reside in a data memory such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of computer-readable storage medium known in the art. A sample storage medium may be coupled to a machine such as, for example, a computer/processor (which may be referred to herein, for convenience, as a “processor”) such the processor can read information (e.g., code) from and write information to the storage medium. A sample storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in user equipment. In the alternative, the processor and the storage medium may reside as discrete components in user equipment. Moreover, in some aspects any suitable computer-program product may comprise a computer-readable medium comprising codes relating to one or more of the aspects of the disclosure. In some aspects a computer program product may comprise packaging materials.

While the invention has been described in connection with various aspects, it will be understood that the invention is capable of further modifications. This application is intended to cover any variations, uses or adaptation of the invention following, in general, the principles of the invention, and including such departures from the present disclosure as come within the known and customary practice within the art to which the invention pertains. 

1. A method for scheduling request operation of a small cell in a wireless communication system, the method comprising: having a user equipment (UE) configured with a first serving cell and a second serving cell; configuring the UE with a first scheduling request (SR) resource on a first physical uplink control channel and a second SR resource on a second physical uplink control channel; selecting, by the UE, the first SR resource to start a SR procedure in response to a trigger by a buffer status report (BSR), wherein an availability to use the first SR resource is nearer to a timing of a triggering of the BSR than the availability of the second SR resource; and sending, by the UE, scheduling requests with the first SR resource on the first physical uplink control channel.
 2. The method of claim 1, further comprising: ignoring, by the UE, the second SR resource for sending scheduling requests.
 3. The method of claim 1, wherein the first serving cell is a Macro Cell and the second serving cell is a Small Cell, or wherein the first serving cell is a Small Cell and the second serving cell is a Macro Cell.
 4. The method of claim 1, wherein the first serving cell and the second serving cell are controlled by different schedulers.
 5. The method of claim 1, wherein the first serving cell and the second serving cell are connected to each other through a non-ideal backhaul.
 6. The method of claim 4, further comprising: starting a prohibit timer upon sending the first scheduling request; and deciding, by the UE, whether a SR resource following the first SR resource is prohibited based on whether the following SR resource and the first SR resource are associated with the same scheduler.
 7. A method for scheduling request operation of a small cell in a wireless communication system, the method comprising: having a user equipment (UE) configured with a first serving cell and a second serving cell; configuring the (UE) with a first scheduling request (SR) resource on a first physical uplink control channel and a second SR resource on a second physical uplink control channel; selecting, by the UE, a first SR resource or the second SR resource to start a SR procedure in response to a trigger by a buffer status report (BSR), wherein the UE uses all SR resources to send scheduling requests; and sending, by the UE, scheduling requests with the first SR resource and the second SR resource on the first and the second physical uplink control channels, respectively.
 8. The method of claim 7, wherein the first and the second SR resources have independent SR procedures.
 9. The method of claim 7, wherein a common SR procedure is used for the first and second SR resources.
 10. The method of claim 7, wherein the first serving cell is a Macro Cell and the second serving cell is a Small Cell, or wherein the first serving cell is a Small Cell and the second serving cell is a Macro Cell.
 11. The method of claim 7, wherein the first serving cell and the second serving cell are controlled by different schedulers.
 12. The method of claim 7, wherein the first serving cell and the second serving cell are connected to each other through a non-ideal backhaul.
 13. The method of claim 11, further comprising: starting a prohibit timer upon sending the first scheduling request; and deciding, by the UE, whether a SR resource is prohibited based on whether the following SR resource and the previously used SR resource are associated with the same scheduler.
 14. A communication device for improving a new carrier type in a wireless communication system, the communication device comprising: a control circuit; a processor installed in the control circuit; a memory installed in the control circuit and operatively coupled to the processor; wherein the processor is configured to execute a program code stored in memory to provide small cell enhancement in a wireless communication system by: having a user equipment (UE) configured with a first serving cell and a second serving cell; configuring the (UE) with a first scheduling request (SR) resource on a first physical uplink control channel and a second SR resource on a second physical uplink control channel; selecting, by the UE, the first SR resource to start a SR procedure in response to a trigger by a buffer status report (BSR), wherein an availability to use the first SR resource is nearer to a timing of the triggering of the BSR than the availability of the second SR resource; and sending, by the UE, scheduling requests with the first SR resource on the first physical uplink control channel.
 15. The communication device of claim 14, wherein the program code is further configured to ignore, by the UE, the second SR resource for scheduling requests. 